Pin grid array socket with kickback force resisting slide plate

ABSTRACT

Disclosed is an unlocking-proof PGA package socket which is so designed that upon the slide plate being put in its locking position for fastening a PGA package to the socket the longest vector of the circular cam member runs beyond the point of contact at which the cam member is put in contact with the slide plate, thereby allowing the kickback to push the cam member in the direction opposite to the direction in which the cam member turns toward unlocking position.

FIELD OF THE INVENTION

The present invention relates to a pin grid array package socket whichcan be used in making a required electric connection between a pin gridarray package (hereinafter abbreviated as “PGA package”) and anassociated electric circuit.

BACKGROUND OF THE INVENTION

A conventional PGA package socket comprises a base housing having aplurality of terminals arranged in the form of a grid and a slide platehaving a corresponding plurality of through holes made in the form of agrid. The slide plate is laid on the base housing, and it is movablebetween the first position in which the lead pins of a PGA package arepermitted to be inserted in the terminal mounts in the base housingwithout substantial force applied to the PGA package and the secondposition in which the lead pins are put in contact with the terminalsmounted in the base housing.

One example of means for moving the slide plate on the base housingcomprises a cam axle extending on the rear lateral edge of the basehousing and a handle positioned on one side of the base housing, andoperatively connected to the cam axle (see Japan Patent ApplicationLaid-Open Nos. 7-142134, 4-319277, 56-125861 and 11-185914). Anotherexample of slide plate driving means comprises a cam member passingthrough the base housing and the slide plate. The cam member has arecess made in its head for accommodating a screwdriver or a small-sizedhexagonal socket wrench. Using such a tool in place of the handle canmove the cam member.

Referring to FIG. 7(a), a PGA package socket has a cam member 10 passingthrough its base housing and slide plate. The cam member 10 is circular,and its circular outer circumference 12 is put partly in contact withthe opposite lateral sides of the cam hole 18 made in the slide plate11.

The pivot axle (broken lines) 13 of the cam member 10 has its center 13a offset from the center 12 a of the circular outer circumference 12 ofthe cam member 10. A hexagonal socket wrench is inserted in thehexagonal hole 14 of the head of the cam member 10 to be rotated in thedirection indicated by arrow A. Then, the situation as shown in FIG.7(b) is brought about, where the slide plate 11 is moved in thedirection as indicated by arrow B.

Specifically the cam member 10 pushes the slide plate 11 by applying thepushing force X to the slide plate 11. When the radial protrusion 15abuts on the retainer 16, rotation of the cam member 10 stops. In thisposition the lead pins of the PGA package are put in contact with theterminals of the socket, so that the kickback force Y may be caused fromthe resultant resilient force of all lead pins as a counter force to thepushing force X (see FIG. 7(b)). The kickback Y increases with theincrease of the number of the terminals or the lead pins of the PGApackage.

As shown in FIG. 7(b), the pushing force X opposes the kickback Y. Foraccidental reasons these forces fail to oppose each other, so that thecam member 10 may be rotated in the direction indicated by arrow C. As aresult the electric connection between the lead pins of the PGA packageand the terminals of the socket is loosened.

In the hope of solving this problem, as shown in FIG. 8(a), a cam member20 has a flat 22 chamfered on one side, on which side the cam member 20pushes the slide plate 21, and is locked in this position. The cammember 20 is not circular, allowing a significant gap to appear betweenthe outer circumference of the cam member 20 and one lateral side of thecam hole 23 in the slide plate 21. Such a significant gap is apt tocause an adverse effect on the function of permitting the force-freeinsertion of the lead pins of a PGA package in the terminal mounts,since the side plate can move upwardly or downwardly. Stilldisadvantageously, the curve-to-flat transient or angular corner 22 a ofthe cam member 20 is apt to be badly loaded when the cam member 20 ismade to rotate from the unlocking position (FIG. 8(b)) to the lockingposition (FIG. 8(a)), and the angular corner 22 a is apt to be deformed.It means the reduction of lifespan of the cam.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a PGA package socketwhich can use a circular cam member while at the same time assuring thatthe circular cam member cannot be displaced toward the unlocked positiononce it has reached its locked position.

To attain this object a pin grid array package socket comprising a basehousing having a plurality of terminals arranged in the form of a gridand a slide plate having a corresponding plurality of through holes madein the form of a grid, the slide plate being laid on the base housing,and being movable between the first position in which the lead pins of apin grid array package are permitted to be inserted in the terminalmounts in the base housing and the second position in which the leadpins are put in contact with the terminals mounted in the base housing,is improved according to the present invention in that the base housinghas a cam member rotatably fitted in the positioning hole made thereinin such a way that rotation of the cam member in a predetermineddirection may allow the outer periphery of the cam member to push thecounter surface of the positioning hole, thereby making the slide platemove to the second position whereupon the longest vector of the cammember is put in an offset position ahead of the contact position atwhich the outer periphery of the cam member is put in contact with thecounter surface of the positioning hole.

The outer periphery of the cam member is circular.

The cam member may be located in a recess of the base housing and have aradial protrusion integrally connected thereto, thereby making the cammember stop by allowing the radial protrusion to be caught by a innerwall of the recess, which is so positioned on the slide plate that theradial protrusion may be caught by the inner wall when the longestvector of the cam member is put in the offset position ahead of thecontact position at which the outer periphery of the cam member is putin contact with the counter surface of the positioning hole.

A pin grid array package socket comprising a base housing having aplurality of terminals arranged in the form of a grid and a slide platehaving a corresponding plurality of through holes made in the form of agrid, the slide plate being laid on the base housing, and being movablebetween the first position in which the lead pins of a pin grid arraypackage are permitted to be inserted in the terminal mounts in the basehousing and the second position in which the lead pins are put incontact with the terminals mounted in the base housing, is improvedaccording to the present invention in that the base housing has a cammember rotatably fitted in the positioning hole made therein in such away that rotation of the cam member in a predetermined direction mayallow the outer periphery of the cam member to push the counter surfaceof the positioning hole, thereby making the slide plate move to thesecond position whereupon the center of the outer periphery of the cammember is displaced an offset distance apart from the center of thepivot axle of the cam member in the predetermined direction.

Other objects, features and advantages of the invention will be apparentfrom the following detailed description taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The invention, together with its objects and the advantages thereof, maybe best understood by reference to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals identify like elements in the figures and in which:

FIG. 1 is a plane view of a PGA package socket according to anembodiment of the present invention in its unlocking position;

FIG. 2 is a plane view of the PGA package socket in its lockingposition;

FIG. 2A is a side view of a pin grid array package;

FIG. 3(a) is an enlarged plane view of the cam member in its unlockingposition whereas FIG. 3(b) is an enlarged plane view of the cam memberin its locking position;

FIG. 4(a) is an enlarged bottom view of a cam member according to anembodiment whereas FIG. 4(b) is an enlarged cross-sectional view of X—Xline of FIG. 4(a);

FIG. 5 is an partial enlarged isometric view of base housing showing therelation of a pivot axle 31 d, recess 31 a and cam member 35;

FIG. 6 is a partial cutaway side plan view of the PGA socket.

FIG. 7(a) is an enlarged plane view of a cam member in its lockingposition in a conventional PGA package socket whereas FIG. 7(b) is anenlarged plane view of the cam member in its unlocking position; and

FIG. 8(a) is an enlarged plane view of a cam member in its lockingposition in another conventional PGA package socket whereas FIG. 8(b) isan enlarged plane view of the cam member in its unlocking position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the invention may be susceptible to embodiment in different forms,there is shown in the drawings, and herein will be described in detail,a specific embodiment with the understanding that the present disclosureis to be considered an exemplification of the principles of theinvention, and is not intended to limit the invention to that asillustrated and described herein.

Referring to FIGS. 1 and 2, a pin grid array package socket 30 comprisesa rectangular base housing 31 and a slide plate 32 lying on the basehousing 31. The base housing 31 has a plurality of terminals 33 aarranged in the form of a grid whereas the slide plate 32 has acorresponding plurality of through holes 33 made in the form of a grid.The slide plate 32 is laid on the base housing 31, permitting the leadpins 61 of a PGA package 60 to be inserted in the through holes 33 whenthe slide plate 32 remains in the first or unlocking position. When theslide plate 32 is moved to the second or locking position, the lead pinsof the PGA package are put in contact with the terminals mounted in thebase housing 31. Thus, electrical connections are made between the leadpins of the PGA package and the terminals of the base housing 31, and atthe same time, the lead pins and the terminals are fastened together.The slide plate 32 has a positioning, or cam, hole 34 made therein, anda cam member 35 is fitted in the cam hole 34.

As shown in FIG. 4(a)(b) and FIG. 5, the cam member 35 has a bearinghole 35 b for slipping on a pivot axle 31 d of the base housing 31, ahexagonal recess 36 made in its head and a radial protrusion 43 made inits bottom.

As shown in FIG. 5, a recess 31 a is formed and includes the pivot axle31 d. There are two inner walls 31 b, 31 c adjoining the pivot axle 31d. As the radial protrusion 43 of the cam member 35 is plunged into therecess 31 a, the travel of the radial protrusion 43 is limited by theinner walls 31 b,31 c. The cam member 35 therefore can be rotated 180degrees clockwise or counterclockwise (as indicated by double-headedarrow E of FIG. 1).

As shown in FIG. 1, the radial protrusion 43 is in the unlockedposition. The cam retainer 50, which may be a separate component orintegral with the slide plate 32, overlaps with the radial protrusion 43to prevent it from coming out. FIG. 6 shows the cross-sectional view ofthe cam retainer 50. A hexagonal socket wrench is inserted in thehexagonal recess 36 of the head of the cam member 35 to be rotatedclockwise. Then, the circumference 40 of the cam member 35 pushes thecounter surface 32 a of the slide plate 32 in the direction indicated bythe arrow F (see FIG. 2) until the cam member 35 has been locked aslater described. The cam member 35 cannot be loosened unless thehexagonal socket wrench is inserted in the hexagonal recess of the cammember 35 to be rotated counterclockwise.

Referring to FIG. 3(a), the outer circumference 40 of the cam member 35is circular, and the pivot axle 41 under the cam member 35 has itscenter 41 a offset from the center 40 a of the outer circumference 40 ofthe cam member 35. In this particular embodiment the cam member 35 mustbe rotated 180 degrees from the unlocking position (see FIG. 3(a) andFIG. 1) to the locking position (see FIG. 3(b) and FIG. 2). As shown inFIG. 3(a), the center 41 a of the pivot axle 41 is positioned somewhat(more than 3 to 5 degrees) clockwise ahead of the line extending fromthe center 40 a of the outer circumference 40 to the point 32 b at whichthe outer circumference 40 of the cam member 35 is put in contact withthe counter surface 32 a of the slide plate 32.

The pushing force M, which is the longest vector, originates from thecenter 41 a of the pivot axle 41 is directed from the center 41 a to theouter circumference 40 of the cam member 35 via the center 40 a of theouter circumference 40. The cam member 35 is rotated 180 degrees toreach the locking position (see FIG. 3(b)), and then, the radialprotrusion 43 of the cam member 35 abuts on the inner wall 31 c. In thisposition, the longest vector M have turned beyond the point of contact32 b where the outer circumference 40 of the cam member 35 is put incontact with the counter surface 32 a.

As described above, when a PGA package is mounted to the socket 30, thecam member 35 is subjected to the kickback force Y from the lead pins ofthe PGA package. The point of the vector M which is directed from thecenter 41 a of the pivot axle 41 to the center 40 a of the outercircumference 40 is so displaced along the counter surface 32 a that thekickback force Y may apply a rotary force (moment) to make the cammember 35 turn clockwise toward the locking position, which is oppositeto the counterclockwise turning toward the unlocking position. Thus,there is no fear of allowing the PGA package to be loosely applied tothe socket 30. Also, advantageously the arrangement permits use of acircular cam member 35, thus assuring that no gap appears between oneside of the cam hole 34 and the outer circumference 40 of the cam member35 except the manufacturing tolerance, and that no adverse effect iscaused on the force-free insertion of lead pins in applying a PGApackage to the socket.

As may be understood from the above, a PGA package socket is so designedaccording to the present invention that upon the slide plate being putin its locking position for fastening a PGA package to the socket thelongest vector of the circular cam member runs beyond the point ofcontact at which the cam member is put in contact with the slide plate,thereby allowing the kickback to push the cam member in the directionopposite to the direction in which the cam member turns toward unlockingposition.

While a preferred embodiment of the present invention is shown anddescribed, it is envisioned that those skilled in the art may devisevarious modifications of the present invention without departing fromthe spirit and scope of the appended claims.

It will be understood that the invention may be embodied in otherspecific forms without departing from the spirit thereof. The presentexamples and embodiments, therefore, are to be considered in allrespects as illustrative and not restrictive, and the invention is notto be limited to the details given herein.

1. A pin grid array package socket for receiving a pin grid arraypackage having a plurality of lead pins, the pin grid array packagesocket comprising: a base housing having a positioning hole and aplurality of terminals arranged in the form of a grid; and a slide platehaving a plurality of through holes made in the form of a gridcorresponding to the plurality of terminals, the slide plate being laidon the base housing, and being movable between a first position in whichthe lead pins are permitted to be inserted in the base housing and asecond position in which the lead pins are put in contact with theterminals mounted in the base housing, characterized in that the basehousing has a cam member rotatably fitted in the positioning hole suchthat rotation of the cam member allows an outer periphery of the cammember to engage a counter surface of the positioning hole, and whereina pushing force directed to the counter surface is directed at aposition offset from the counter surface such that a kickback force willnot move the slide plate from the second position to the first position.2. The pin grid array package socket according to claim 1 wherein theouter periphery of the cam member is circular.
 3. The pin grid arraypackage socket according to claim 1 wherein the cam member includes aradial protrusion to limit the rotation of the cam member.
 4. The pingrid array package socket according to claim 1, wherein the base housingincludes a recess for receiving the cam member.
 5. The pin grid arraypackage socket according to claim 4, wherein the recess includes atleast one inner wall, the inner wall acting to limit the travel of thecam member.
 6. The pin grid array package socket according to claim 1,wherein the cain member is retained within the positioning hole by a camretainer.
 7. The pin grid package socket according to claim 6, whereinthe cam retainer is integral with the slide plate.
 8. The pin gridpackage socket according to claim 1, wherein the cam member rotatesaround a pivot axle.
 9. The pin grid package socket according to claim8, wherein a center point of the pivot axle is offset from a center ofan outer circumference of the cam member.
 10. The pin grid packagesocket according to claim 1, wherein the cam member includes a recessfor receiving a tool to rotate the cam member between the first positionand the second position.
 11. The pin grid package socket according toclaim 10, wherein the cam member recess is hexagonal.